This invention relates in general to coal handling equipment and more particularly to a machine for breaking frozen lumps of coal.
Much of the coal that is mined in this country is delivered to users in open railway cars or barges. As it leaves the mines this coal is normally in a lump size which is easily handled by conveyors and other handling equipment. However, during the long rail or barge journey the coal may pass through rain and snow storms and acquire a considerable amount of moisture. This does not present much of a problem during the spring, summer and fall, but in winter the moisture often freezes and bonds the small lumps together into large massive lumps which block and disrupt handling equipment. For example, a large lump will not rise along a steeply inclined belt conveyor, but instead will tumble downwardly and carry much of the other coal along with it. Also, large frozen lumps of coal tend to lodge in restricted areas of the conveying equipment, where they produce jams that disrupt the equipment.
To facilitate the handling of coal during winter months frozen coal crackers were developed. The typical frozen coal cracker is a large machine containing a rotor that is provided teeth which pass by a breaker plate. Coal that is dumped into the machine must pass between the cutting teeth and the breaker plate, and of course any large frozen lumps of coal will be broken or cracked to a size suitable for handling. Only during the winter does the machine serve any purpose. During the warmer months the machine merely stands idle with its breaker plate backed off from the rotor so that the coal passes freely through the machine. This, however, causes unnecessary wear on the rotor, and indeed, the wear caused by the free falling coal often exceeds the wear caused from breaking frozen lumps. For this reason, some operators run their coal crackers during the warmer months, merely to reduce the wear and to distribute it more evenly, but this consumes energy and certainly does not eliminate the wear. Other operators remove the rotors from their machines during the warmer months so that the coal passes through the machine housing without encountering the rotor. The rotor for a typical frozen coal cracker, however, is quite heavy, and furthermore the back of the machine and the drive train must be dismantled to free the rotor. This requires a considerable amount of labor.
One system which solves the problem has a carriage on which both a frozen coal cracker and a by-pass chute are mounted, and this carriage shifts such that either the by-pass chute or the frozen coal cracker may be positioned to receive the coal. During warm weather the by-pass chute receives the coal so that the falling coal does not encounter the frozen coal cracker. When temperatures drop below freezing, the carriage is shifted to position the frozen coal cracker for processing the coal. See U.S. Pat. No. 4,205,795. The carriage and the track on which it moves consume a large amount of space, and therefore this system is not satisfactory where space is limited.